Antenna



- March 10, 1942. H: O PETERSON 2,275,646

ANTENNA Filed July 18, 1939 2 Sheets-Sheet l INV EN TOR. TERSON BY ATTORNEY.

March 10, 1942. H O. PETERSQN 2,275,646

ANTENNA Filed July 18, 1939 2 Sheets-Sheet 2 INVEN TOR.

ATTORNEY.

Patented Mar. 10, 1942 AN TENNA.

Harold 0. Peterson, Riverhead, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application July 18, 1939, Serial No. 285,066

3 Claims.

and, more particularly, with ultra short wave directive antennas.

An object of the present invention is to obtain Q improved directivity in an ultra short wave antenna system. 1

Another object of the present invention is to provide a directive antenna having a symmetri cal radiating system and which may be energized from a single sided coaxial feeder.

Another object of the present invention is to provide an antenna system which does not require transformers for coupling between a coaxial transmission line and a symmetrical radiating system.

Still another object of the present invention is the provision of an antenna structure which is mechanically secure and is safeguarded against lightning strokes.

The present invention features an antenna array within a parabolic reflector in order to obtain a directional radiation pattern. In order to further increase directivity by reducing random phase relationship between the signals radiated from the various antennae of the array metallic partitions are provided within the reflector between the antennae.

As another feature of the invention in order to obtain as wide a frequency band as possible I may use conical radiating elements. The elements of the array are each energized by transmission lines of equal length thereby assuring proper phase relationship for any frequency within the band. Furthermore, by a proper proportioning of the dimensions I avoid the use of conventional frequency-discriminatory impedance matching circuits between the elements of the antenna and the transmission line connected thereto.

.As still a further feature of the invention I provide a mechanically strong and electrically efficient means for transforming from a single sided coaxial cable to a symmetrical radiating circuit.

Other objects and features of the invention will become apparent by reference to the following detailed description which is accompanied by drawings in which Figure 1 shows in section an elevation of my improved antenna system; Figure 2 shows a horizontal sectional view of the form of my invention shown in Figure 1; Figure 3 shows a modification of the form of my invention shown in Figure 1 inwhich impedance matching means are employed between the ladiating element and the transmission line energizing the radiating element; in Figure 4 I have shown'a further modification of my invention in which a single sided transmission line is coupled to a symmetrical radiating system; Figure 5 shows in enlarged section a portion of Figure 4,

have placed metallic partitions 13.

while Figure 6 shows a modification of the form shown in Figure 5. 1

Referring, now, to Figure 1 reference numerals l, I indicateradiating elements of my antenna array. These radiating elements are placed at the focus of parabolic reflector 2. The parabolic reflector is closed at the ends by plates 3, 3. To successive ones of the radiating elements I are connected transmission lines 4, 5, 6 and 1. These line sections are of equal length and at their points of junction are connected to transmission line [0 through linesections 8 and 9 which are also of equal length. It will, therefore, be seen that the total length of connections between transmission line 10 and each of the radiating elements is the same. Therefore, the phase relationships are maintained constant no matter what frequency is applied to the transmission line. Between each of the radiating elements I These metallic partitions confine the signal radiated from each of the radiating elements into a definite area and thus a uniform phase relationship is obtained in the area immediately beyond the open side of the reflector. Due to this uniform phase relationship an improvement in directivity is obtained. In other words, less response is obtained for directions away from the main lobe of the directive diagram.

Figure ,2 shows more clearly the relationship between the parabolic reflector 2 and the radiating element I.

In Figure 3 I have shown a modification of a portion of the embodiment. shown in Figure 1. The same form of radiating element l is utilized as described with reference to Figure 1. Also, the radiating elements are each confined between partitions l3, I3. as before described. modification the radiating element I, having 'a length approximately equal to three-eighths of,

the length of the operating wave at its apex, is connected to central conductor l5 of transmission line 5 within pedestal 3i. The height of this pedestal 3| is considerably .less than a quarter of the length of the operating wave.

The impedance of the transmission line is smoothly transformed to a value equal to that of the radiator without affecting the band width by gradually tapering the central conductor I5 into radiator l. The diameter of the inner surface of pedestal 3| is likewise tapered. By arranging a constant change of ratio of the diameter of the central conductor and inner surface of the pedestal, a smooth transformation of impedance is obtained. While Figure 3 shows only one radiating element, of course, any desired number may be used and the transmission lines are preferably connected together in the same way as described with reference to Figure 1. With this form of connection and; utilizing this In this ure 1.

shape 'of radiating element an extremely broad frequency band may be covered with substantially uniform response.

In Figures l and I have shown a balanced or symmetrical radiating system substituted for the single sided radiating elements shown in Fig- The radiating system within each compartment of the reflector comprises a pair of quarter wave rods 4H, 43. These are energized in an opposing phase relationship at their adjacent ends by a phase inverting circuit within cylinder ll. This coupling and inverting circuit includes two cylindrical members i5 and iBhaving equal diameters and being somewhat greater than a quarter of the operating wave-length in length. The cylinder "iii may conveniently be an extension or the outer casing 5 of the concentric cable transmission line. The inner conductor 15 of the coaxial transmission ,line is connected to the end of cylinder; Mi and the two radiating elements d5, 35 are directly connected to the adjacentends of cylinders 25 and 46. Within outer cylinder 81 are also located two shorting plates 4'3 and 45 making contact between the. inner surface of cylinder 5? and the outer surfaces of cylinders '35 and d6. adjustable in their positionand are adjusted to a position a quarter of the length of the operating wave distant from the adjacent ends of cylinders 55 and M3. Adjusted to this position the impedance of the'outer shell at points e, e to the operating frequency may be made very high compared with the impedance of the eoncentric feeder line 5, l5 and the impedance of the antenna elements 4! at those'points By a.

proper choice of the ratio of diameters of cylinder ll and cylinders 45, iii, the concentric ,'H1'18 and the coupling circuit may be made. to

have the same impedance as the antenna'elements as viewed at points i, i. Each of the plurality of balanced radiating systems just described with reference to Figure 5 is, as shown in Figure '4, connected to transmission line l8, 1 l by uniform length connections. Thus, as previously described, a uniform phase relationship is maintained'throughout. The final impedance at the junction of connection lines 8 and 9 may or may not exactlyagree with the impedance of the transmission line it, ii. If not, an additional section of transmission line 60, 61 may, therefore, be interposed between these two lines. By a choice of proper dimensions of the taper of inner conductor El with respect to the diameter of the outer conductor 59, the impedance may be made to match perfectly. The distance m is ordinarily fixed at several quarter wavelengths of the operating wave. With this form of impedance matching structure no restriction in the band width of the antenna itself is obtained.

In Figure 6 is shown the adaptation of the conical radiating elements to the structure shown in Figure 5 fortransforming from a single sided cable to a symmetrical circuit. It is not believed necessary to describe this figure in any detail since the distinction between this and Figure 5 is the use of the conical radiators having a length equal to three-eighths of the operating ited thereto but that modifications may be made within the scope of the invention.

I claim:

1. A directive antenna system comprising a cylindrical reflector divided longitudinally into a series of separate chambers and a radiating element within each of said chambers, each of said radiating elements comprising a dipole antenna having a pair of adjacent ends and means for energizing said dipole from a coaxial transmission line having an outer sheath and an inner conductor comprising a supportingshell surrounding a portion of said transmission line and attached These shorting plates are at one end to said reflector, said shell having a length greater than half the length of the operating wave, an auxiliary conductor within said shell connected to the inner conductor of said transmission line, and having a'diameter equal to the diameter of the outer sheath'of said transmission line, the adjacent ends of said dipole passing through apertures in said supporting shell and connected to the adjacent ends of said sheath and said auxiliary conductor, and means for connecting the inner surface of said supporting shell to the outer surface of said sheath and auxiliary conductor at points a distance equal to a quarter of the length of the operating wave from said adjacent ends.

2. A directive antenna system comprising a cylindrical reflector divided longitudinally into a series of separate chambers and a radiating element within each of said chambers, each of said radiating elements comprising a dipole antenna parallel to the axis of said reflector having a pair of adjacent ends, and means for energizing said dipole from a coaxial transmission line having an outer sheath and an inner conductor comprising a a supporting shell surrounding a portion of said transmission line, and attached at one end to said reflector, said shell having alength greater than half the length of the operating wave, an, auxiliary conductor within said shell connected to the inner conductor of said transmission line and having a diameter equal to the diameter of the outer sheath of said transmission line, the adjacent ends of said dipole passing through apertures in said supporting shell and connected to the adjacent ends of said sheath and saidauxiliary conductor, and means for connecting the inner surface of said supporting shell to the outer surface of said sheath and auxiliary conductor at points a distance equal to a quarter of the lengthof the operating Wave from said adjacent ends.

3. Means for feeding energy to'a pair of adjacent ends of a dipole antenna from a coaxial transmission line having an outer sheath and an inner conductor comprising a supporting shell surrounding a portion of said transmission line, said shell having a length greater than half the length of the operating wave, an auxiliary conductor within said shell connectedto the inner conductor of said transmission line and having a diameter equal to the diameter of the outer sheath of said transmission line, the adjacent ends of said dipole passing through apertures in, said supporting shell and connected to the adjacent ends of said sheath and said auxiliary conductor, and means for connecting the inner surface of said supporting shell to the outer surface of said sheath and auxiliary conductor at HAROLD o. PETERSON. 

